International detectives involved in domestic killing (8)
I believe the answer is:
homicide
'killing' is the definition.
(homicide is a kind of killing)
'international detectives involved in domestic' is the wordplay.
'international' becomes 'i' (abbreviation eg in IMF).
'detectives' becomes 'cid'.
'involved in' indicates putting letters inside.
'domestic' becomes 'home' ('home' can be similar in meaning to 'domestic').
'i'+'cid'='icid'
'icid' placed inside 'home' is 'HOMICIDE'.
(Other definitions for homicide that I've seen before include "The killing of one person by another" , "Serious crime" , "Manslaughter or murder" , "The killing of a human (mainly US)" , "Murder (of one person)" .)